The lactic acid bacteria live in the intestines of mammals and prevent abnormal fermentation by saprophytes. Thus, they are utilized as medicine for intestinal disorders. For example, L. bulgaricus is the lactic acid bacteria that have been known from long ago. It is used for the production of yogurt and also as a starter when producing cheese or cultured butter. And, the aerobic lactic acid bacteria L. acidophilus, which is found in the intestines of all mammals including human and other animals, is used for the production of butter or milk or for the treatment of autointoxication. Meanwhile, L. lactis produces d- and l-lactic acids. It is used for the production of butter or cheese, and is the most important lactic acid bacteria for dairying. In addition, lactobacillus bifidus is also well known. A large number of lactobacillus bifidus is found particularly in the intestines of breast-fed infants, and the number is gradually reduced while the infants grow. As such, it is regarded as being important for the health in early childhood. Also, like the other lactic acid bacteria, its fermentation product generates organic acid and antibacterial active materials to inhibit harmful intestinal bacteria. Currently, research is being actively conducted on lactic-acid fermented milk using lactobacillus bifidus, and products to be added to powdered formula to improve the health of formula-fed infants.
The lactic acid bacteria settle in the intestine and provide various physiological activities, including activation of intestinal movement, inhibition of harmful bacteria, promotion of synthesis of vitamins and immunostimulants, and the like. When orally taken, lactic acid bacteria tend to be killed by gastric acid or bile acid and do not exert their physiological activities.
In order to solve this problem, techniques for coating lactic acid bacteria have been developed. Conventional techniques for coating lactic acid bacteria include enteric-coated lactic acid bacteria using capsules and microencapsulated lactic acid bacteria using gelatin, sugar, gum, and the like.
Specifically, the conventional techniques for coating lactic acid bacteria are characterized by a separate coating process followed by collecting process of lactic acid bacteria. More specifically, the conventional lactic acid bacteria coating process is performed by adding an aqueous coating composition capable of forming ultrafine spherical beads to lactic acid bacteria powder, and performing stirring, mixing and freeze-drying.
Because the conventional techniques for coating lactic acid bacteria include collecting cultured lactic acid bacteria and making them into powder after drying, followed by mixing with a coating composition and stirring, they are associated with the following problems. The use of expensive coating agent and addition of the coating process result in increased production cost. Further, aseptic manipulation is difficult because other bacteria may be included. Besides, use of cryoprotectant and stabilizer during a freeze-drying process followed by coating process for ensuring superior viability and stability may result in interactions between materials or redundancy of processes.
In order to solve these problems, the present inventors have filed a patent related to a method for preparing double-coated lactic acid bacteria with improved bacterial stability and processing stability through prevention of direct interaction with air and moisture and through enhanced heat resistance, acid resistance and bile resistance have been developed (Korean Patent Application No. 2001-0010397) and a patent related to a method for preparing triple-coated lactic acid bacteria further improved from the double-coated lactic acid bacteria (Korean Patent Application No. 2008-0008267).
However, the above improved techniques for coating lactic acid bacteria may be appropriated used in powder-type products but may not sufficiently prevent killing of lactic acid bacteria by moisture in watery foods. Hence, they can be used only in restrictive fields against a broad range of foods.
Meanwhile, edible oils and fats are obtained from animals such as cows, pigs, and sheep and various oily seeds by using a refining method, a press method, or an extraction method using an organic solvent. Most edible oils and fats are hardly melted in water and alcohol and are melted well in an organic solvent such as ether or benzene. Also, their specific gravity is less than that of water. According to the type of fatty acid, if the content of an unsaturated fatty acid is high, it has a low melting point and is in a liquid state at room temperature. If the content of a saturated fatty acid is high, it has a high melting point and thus is in a solid state at room temperature. Due to the above characteristics, if lactic acid bacteria are coated with an edible oil/fat, they may prevent water contact to a certain level and may be used in various food groups.
However, due to difficulties of processing, any edible oil/fat has not been used as a coating agent of lactic acid bacteria.
As such, the present inventors have added an edible oil/fat as a coating agent of lactic acid bacteria conventionally coated with protein, polysaccharide, and nanoparticles so as to further improve heat resistance, acid resistance, and bile resistance of the lactic acid bacteria, and particularly to effectively increase stability against a moisture variation, thereby completing the present invention.